1. Field of the Invention
This invention relates to new polyurethaneurea compositions comprising poly(tetramethylene-co-ethyleneether) glycols comprising constituent units derived by copolymerizing tetrahydrofuran and ethylene oxide, wherein the portion of the units derived from ethylene oxide is present in the poly(tetramethylene-co-ethyleneether) glycol from greater than about 37 to about 70 mole percent and the number average molecular weight is from about 1900 Dalton to about 4000 Dalton. The invention further relates to the use of poly(tetramethylene-co-ethyleneether) glycols having such high number average molecular weights as the soft segment base material in spandex compositions. The invention also relates to new polyurethane compositions comprising poly(tetramethylene-co-ethyleneether) glycols having such high number average molecular weight and their use in spandex.
2. Description of the Related Art
Poly(tetramethylene ether) glycols, also known as polytetrahydrofuran or homopolymers of tetrahydrofuran (THF, oxolane) are well known for their use in soft segments in polyurethaneureas. Poly(tetramethylene ether) glycols impart superior dynamic properties to polyurethaneurea elastomers and fibers. They possess very low glass transition temperatures, but have crystalline melt temperatures above room temperature. Thus, they are waxy solids at ambient temperatures and need to be kept at elevated temperatures to prevent solidification. As the molecular weight of poly(tetramethylene ether) glycols increase, their melt temperatures increase. The melting point of the glycol limits the molecular weight of the poly(tetramethylene ether) glycols that can be used to make spandex. As the melting point of the soft segment rises above ambient temperature, the set increases rapidly and the retractive power drops due to the increased crystallinity of the soft segment. Therefore the maximum molecular weight of poly(tetramethylene ether) glycols that can be used as a soft segment material is limited to that molecular weight that results in a melting point at or slightly above the use temperature of the spandex. In practice, the upper limit of poly(tetramethylene ether) glycols molecular weight useful in spandex is 1800 to 2000 Dalton, corresponding to a glycol melting point of about 26 to 30° C.
Copolymerization with a cyclic ether has been used to reduce the crystallinity of the polytetramethylene ether chains. This lowers the polymer melt temperature of the copolyether glycol and at the same time improves certain dynamic properties of the polyurethaneurea that contains such a copolymer as a soft segment. Among the comonomers used for this purpose is ethylene oxide, which can lower the copolymer melt temperature to below ambient, depending on the comonomer content. At ethyleneether contents above about 15 mole percent, the poly(tetramethylene-co-ethyleneether) glycols are moderately viscous liquids at room temperature. As the ethyleneether content increases above 15 mole percent, the melting point decreases further. Use of poly(tetramethylene-co-ethyleneether) glycols may also improve certain dynamic properties of polyurethaneureas, for example tenacity, elongation at break, and low temperature performance, which is desirable for some end uses.
Poly(tetramethylene-co-ethyleneether) glycols are known in the art. Their preparation is described in U.S. Pat. Nos. 4,139,567 and 4,153,786. Such copolymers can be prepared by any of the known methods of cyclic ether polymerization, such as those described in “Polytetrahydrofuran” by P. Dreyfuss (Gordon & Breach, N.Y. 1982), for example. Such polymerization methods include catalysis by strong proton or Lewis acids, heteropoly acids, and perfluorosulfonic acids or acid resins. In some instances it may be advantageous to use a polymerization promoter, such as a carboxylic acid anhydride, as described in U.S. Pat. No. 4,163,115. In these cases, the primary polymer products are diesters, which then need to be hydrolyzed in a subsequent step to obtain the desired polymeric glycols.
Poly(tetramethylene-co-ethyleneether) glycols offer advantages over poly(tetramethylene ether) glycols in terms of certain specific physical properties. At ethyleneether contents above 20 mole percent, the poly(tetramethylene-co-ethyleneether) glycols are moderately viscous liquids at room temperature and have a lower viscosity than poly(tetramethylene ether) glycols of the same molecular weight at temperatures above the melting point of poly(tetramethylene ether) glycols. Certain physical properties of the polyurethanes or polyurethaneureas prepared from poly(tetramethylene-co-ethyleneether) glycols surpass the properties of those polyurethanes or polyurethaneureas prepared from poly(tetramethylene ether) glycols.
Spandex based on poly(tetramethylene-co-ethyleneether) glycols is also known in the art. However, most of these are based on poly(tetramethylene-co-ethyleneether) containing co-extenders or extenders other than ethylene diamine. U.S. Pat. No. 4,224,432 to Pechhold et al. discloses the use of poly(tetramethylene-co-ethyleneether) glycols with low cyclic ether content to prepare spandex and other polyurethaneureas. Pechhold teaches that ethyleneether levels above 30 percent are preferred. Pechhold does not teach the use of coextenders, though it discloses that mixtures of amines may be used.
U.S. Pat. No. 4,658,065 to Aoshima et al. discloses the preparation of several THF copolyethers via the reaction of THF and polyhydric alcohols using heteropolyacid catalysts. Aoshima also discloses that copolymerizable cyclic ethers, such as ethylene oxide, may be included with the THF in the polymerization process. Aoshima discloses that the copolyether glycols may be used to prepare spandex, but contains no examples of spandex from poly(tetramethylene-co-ethyleneether) glycols.
U.S. Pat. No. 3,425,999 to Axelrood et al. discloses the preparation of polyether urethaneureas from poly(tetramethylene-co-ethyleneether) glycols for use in oil resistance and good low temperature performance. The poly(tetramethylene-co-ethyleneether) glycols have ethyleneether content ranging from 20 to 60 percent by weight (equivalent to 29 to 71 mole percent). Axelrood does not disclose the use of these urethaneureas in spandex. Axelrood discloses that “the chain extenders most useful in this invention are diamines selected from the group consisting of primary and secondary diamines and mixtures thereof.” Axelrood further discloses that “the preferred diamines are hindered diamines, such as dichlorobenzidine and methylene bis(2-chloroaniline).” Use of ethylene diamine is not disclosed.
U.S. Pat. No. 6,639,041 to Nishikawa et al. discloses fibers having good elasticity at low temperature that contain polyurethaneureas prepared from polyols containing copolyethers of THF, ethylene oxide, and/or propylene oxide, diisocyanates, and diamines and polymers solvated in organic solvents. Nishikawa teaches that these compositions have improved low temperature performance over standard homopolymer spandexes. In addition, Nishikawa teaches that “the slight variation in copolyether glycol molecular weights is believed to have little effect on polyurethaneurea properties” in describing the data in Table III in which there is a 478 Dalton molecular weight difference between the examples.
The applicants have observed that spandex with high number average molecular weight glycols (i.e., from about 1900 Dalton to about 4000 Dalton) as the soft segment base material provides improved physical properties over spandex prepared from lower number average molecular weight ethyleneether-containing poly(tetramethylene-co-ethyleneether) glycols. The high number average molecular weight glycol-containing spandex of the present invention demonstrates lower set, load power, higher unload power, higher elongation, and higher circular knitting total draft than lower number average molecular weight ethyleneether spandex. Therefore, for several end uses a high molecular weight poly(tetramethylene-co-ethyleneether) glycol-containing spandex would be preferred over a lower molecular weight poly(tetramethylene-co-ethyleneether) glycol-containing spandex.